U.S. patent application number 15/133323 was filed with the patent office on 2017-04-13 for integratable planar waveguide type non-reciprocal polarization rotator.
The applicant listed for this patent is INHA-INDUSTRY PARTNERSHIP INSTITUTE. Invention is credited to Dong Wook KIM, Kyong Hon KIM, YuDeuk KIM, Moon Hyeok LEE.
Application Number | 20170102565 15/133323 |
Document ID | / |
Family ID | 56939310 |
Filed Date | 2017-04-13 |
United States Patent
Application |
20170102565 |
Kind Code |
A1 |
KIM; Kyong Hon ; et
al. |
April 13, 2017 |
INTEGRATABLE PLANAR WAVEGUIDE TYPE NON-RECIPROCAL POLARIZATION
ROTATOR
Abstract
The present invention describes a planar waveguide-type
integrated non-reciprocal polarization rotator. According to an
embodiment of the present invention, the planar waveguide-type
non-reciprocal 90.degree. polarization rotator includes optical
waveguide-type input and output ports, a reciprocal 45.degree.
polarization rotator based on an asymmetric optical waveguide
structure, a non-reciprocal 45.degree. polarization rotator based
on an optical waveguide with a clad layer of magneto-optic
material, and a phase compensator placed between the above
reciprocal 45.degree. polarization rotator and non-reciprocal
45.degree. polarization rotator compensating the phase difference
between two polarization modes.
Inventors: |
KIM; Kyong Hon; (Incheon,
KR) ; KIM; YuDeuk; (Incheon, KR) ; KIM; Dong
Wook; (Seoul, KR) ; LEE; Moon Hyeok; (Incheon,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INHA-INDUSTRY PARTNERSHIP INSTITUTE |
Incheon |
|
KR |
|
|
Family ID: |
56939310 |
Appl. No.: |
15/133323 |
Filed: |
April 20, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 6/2766 20130101;
G02F 1/0136 20130101; G02F 1/0955 20130101; G02B 6/126
20130101 |
International
Class: |
G02F 1/095 20060101
G02F001/095; G02B 6/126 20060101 G02B006/126; G02F 1/01 20060101
G02F001/01; G02B 6/27 20060101 G02B006/27 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 21, 2015 |
KR |
10-2015-0055914 |
Claims
1. An integrated planar waveguide-type non-reciprocal 90.degree.
polarization rotator comprising: optical waveguide-type input and
output ports; a reciprocal 45.degree. polarization rotator based on
an asymmetric optical waveguide structure; a non-reciprocal
45.degree. polarization rotator based on an optical waveguide with
a clad layer of magneto-optic material; and a phase compensator
placed between the above reciprocal 45.degree. polarization rotator
and non-reciprocal 45.degree. polarization rotator compensating the
phase difference between two polarization modes.
2. The integrated planar waveguide-type non-reciprocal 90.degree.
polarization rotator of claim 1 wherein the clad layer of
magneto-optic material comprises a magneto-optic polymer.
3. The integrated planar waveguide-type non-reciprocal 90.degree.
polarization rotator of claim 1 further comprising a magnetic
material layer formed on the top of the clad layer in the
non-reciprocal 45.degree. polarization rotator.
4. The integrated planar waveguide-type non-reciprocal 90.degree.
polarization rotator of claim 1 wherein the reciprocal 45.degree.
polarization rotator comprises an optical waveguide whose one side
is etched and whose both ends are connected to tapered waveguides
to reduce optical losses.
5. The integrated planar waveguide-type non-reciprocal 90.degree.
polarization rotator of claim 1 wherein the phase compensator
controls the phase of each polarization mode by using the
difference between the effective indices of two orthogonal
polarizations with different width (W4) and height (H4) of the
optical waveguide, and has tapered waveguide ends at both sides in
a case that the width of the optical waveguide in the phase
compensator is different from those of the optical waveguides
connected at its both ends.
6. The integrated planar waveguide-type non-reciprocal 90.degree.
polarization rotator of claim 1 further comprising a pair of the
polarization beam splitter and combiner attached at the both input
and output ends of its optical waveguides so that the whole acts as
an optical isolator.
7. The integrated planar waveguide-type non-reciprocal 90.degree.
polarization rotator of claim 1 further comprising: optical
waveguide-type input and output ports; a reciprocal 45.degree.
polarization rotator based on an asymmetric optical waveguide
structure; a non-reciprocal 45.degree. polarization rotator based
on an optical waveguide with a clad layer of magneto-optic
material; and a phase compensator placed between the above
reciprocal 45.degree. polarization rotator and non-reciprocal
45.degree. polarization rotator compensating the phase difference
between two polarization modes; a pair of the polarization beam
splitter and combiner attached to the planar waveguide-type
non-reciprocal 90.degree. polarization rotator so that the whole
performs a function of a polarization-insensitive optical isolator.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Patent
Application No. 10-2015-0055914, filed with the Korean Intellectual
Property Office on Apr. 21, 2015, the disclosure of which is
incorporated herein by reference in its entirety.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention describes an integratable planar
waveguide-type non-reciprocal polarization rotator. As an
embodiment of the present invention, the planar waveguide-type
non-reciprocal 90-degree polarization rotator includes optical
waveguide-type input and output ports; a reciprocal 45-degree
polarization rotator of an asymmetric optical waveguide structure;
an optical waveguide-type non-reciprocal 45-degree polarization
rotator with cladding layer of magneto-optic material; and a phase
compensator which compensates the phase difference between
polarizations by having positioned between the above reciprocal
45-degree polarization rotator and non-reciprocal 45-degree
polarization rotator.
[0004] 2. Description of the Related Art
[0005] On-chip-type non-reciprocal polarization rotators are
important optical devices for future applications to integrated
optical isolators and circulators and to various polarization
sensors.
[0006] The non-reciprocal polarization rotator is an optical device
rotating the polarization of an optical beam traveling in one
direction by 90 degrees, but passing another optical beam traveling
in the opposition direction without changing its polarization. The
non-reciprocal polarization rotator can be used for applications to
optical isolators and optical circulators by having polarization
filters or polarization beam splitters combined at its input and
output ports.
[0007] The optical isolators based on the non-reciprocal
polarization rotator utilizing Faraday rotation function of the
magneto-optic effect in bulk-optics have been used popularly.
However, various approaches for integrated planar waveguide-type
non-reciprocal polarization rotators, which can be integrated with
other photonic devices, are still under development and not ready
for a practical optical isolator of integration-type.
[0008] The conventional art of US 2013/0142475 describes an
integrated non-reciprocal polarization rotator and an integrated
optical isolator utilizing the integrated reciprocal and
non-reciprocal polarization rotators, which have a block of
magneto-optic material, such as bismuth europium holmium gallium
iron garnet or bismuth yttrium iron garnet, located between two
silicon waveguides, an index-matching layer formed between the
silicon waveguide and magneto-optic material, and a magnetic field
applied to the magneto-optic material by attaching a magnet. This
prior art uses a scheme of 45.degree. polarization rotation in the
reciprocal polarization rotator section and additional 45.degree.
polarization rotation in the non-reciprocal polarization rotator
section. However, this art requires a difficult fabrication process
to form an index-matching layer between the silicon waveguide and
magneto-optic material, and has a significant drawback of a high
optical loss over the entire device.
[0009] Another prior art of the non-reciprocal polarization rotator
has been demonstrated by using birefringence between two orthogonal
polarization modes in an InGaAsP optical waveguide of asymmetric
square shape with one side of inclined surface, which includes a
hybrid integration of Ce:YIG crystal formed on the top of the
waveguide and a magnetic field applied in an orthogonal direction
to the light propagation direction [IEEE J. Quantum Electronics
46(11), 1662(2010)]. In this art, the etching control is not easy
to form the asymmetric InGaAsP optical waveguide and a uniform
bonding process of the magneto-optic crystal is difficult. Thus,
this art has a drawback of low efficiency of the Faraday
polarization rotation.
[0010] A prior art of a reciprocal polarization rotator describes
reciprocal polarization rotation in a GaInAsP or Si waveguide
having a long asymmetric trench pattered inside the waveguide [Opt.
Express 17(14), 11267 (2009) & Opt. Commun. 324. 22 (2014)]. In
this art, a long asymmetric trench is formed in the semiconductor
waveguide, and the waveguide rotates the TE polarization mode into
TM polarization mode for an optical beam travelling in either
direction. However, this art cannot provide the function of
non-reciprocal polarization rotation.
[0011] Another prior art of the reciprocal polarization rotator is
proposed by numerical simulation on reciprocal 90.degree.
polarization rotation in a silicon nanowire waveguide with a
partially etched section [J. Opt. Soc. Am. B 25(5), 747 (2008)].
This prior art describes only a scheme of reciprocal polarization
rotation for optical beams in both directions, but cannot provide
the function of non-reciprocal polarization rotation.
SUMMARY OF THE INVENTION
[0012] The present invention provides a planar waveguide-type
non-reciprocal polarization rotator which has a low insertion loss
and an excellent integration property with laser diode and with
other optical signal processing devices into a single integrated
device. The present invention of the planar waveguide-type
non-reciprocal polarization rotator consists of a reciprocal
polarization rotator which rotates the polarization of an incoming
beam by 45.degree. reciprocally with a birefringence induced by an
asymmetric structure of semiconductor optical waveguide and a
non-reciprocal polarization rotator which rotates the polarization
by 45.degree. non-reciprocally with a symmetric optical waveguide
having an upper clad of magneto-optic (MO) material and a magnetic
field applied from top. This invented device provides a
non-reciprocal function by rotating the polarization of the optical
beam traveling in one direction to 90.degree., but by transmitting
the optical beam traveling in the opposite direction without
rotating its polarization. This invention allows a silicon-on-oxide
(SOI) wafer based planar waveguide-type non-reciprocal polarization
rotator with an easy integration, low insertion loss, large
polarization extinction ratio (PER), and wide operation
bandwidth.
[0013] According to an embodiment of the present invention, a
planar waveguide-type non-reciprocal 90.degree. polarization
rotator is provided. The non-reciprocal polarization rotator
includes optical waveguide-type input and output ports, a
reciprocal 45.degree. polarization rotator based on an asymmetric
optical waveguide structure, a non-reciprocal 45.degree.
polarization rotator based on an optical waveguide with a clad
layer of magneto-optic material, and a phase compensator placed
between the above reciprocal 45.degree. polarization rotator and
non-reciprocal 45.degree. polarization rotator compensating the
phase difference between two polarization modes.
[0014] The clad layer of magneto-optic material in the above planar
waveguide-type non-reciprocal 90.degree. polarization rotator can
comprise a magneto-optic polymer.
[0015] The clad layer of the non-reciprocal 45.degree. polarization
rotator in the above planar waveguide-type non-reciprocal
90.degree. polarization rotator can be covered with a layer of
magnetic material.
[0016] The reciprocal 45.degree. polarization rotator in the above
planar waveguide-type non-reciprocal 90.degree. polarization
rotator can consist of an optical waveguide with a partially etched
section and tapered end structures patterned after an etching
process.
[0017] The phase compensator in the above planar waveguide-type
non-reciprocal 90.degree. polarization rotator can be formed with
an optical waveguide of different width (W4) and height (H4) to
control the phases of polarization components based on the
refractive index difference between two orthogonal polarization
modes, and with two ends of tapered structures when the optical
waveguide width of the phase compensator is different from those
connected at its both ends.
[0018] The above planar waveguide-type non-reciprocal 90.degree.
polarization rotator can act as an optical isolator by attaching a
pair of polarization beam splitter and combiner to the input and
output ports.
[0019] According to another embodiment of the planar waveguide-type
non-reciprocal polarization rotator of the present invention, it
includes optical waveguide-type input and output ports, a
reciprocal 45.degree. polarization rotator based on an asymmetric
optical waveguide structure, a non-reciprocal 45.degree.
polarization rotator based on an optical waveguide with a clad
layer of magneto-optic material, a phase compensator placed between
the above reciprocal 45.degree. polarization rotator and
non-reciprocal 45.degree. polarization rotator compensating the
phase difference between two polarization modes, and a pair of
polarization beam splitter and combiner attached to the input and
output ports to act as an polarization-insensitive optical
isolator.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a plan view of a schematic diagram of a planar
waveguide-type non-reciprocal 90.degree. polarization rotator,
according to an embodiment of the present invention.
[0021] FIG. 2A is a cross-sectional view of a reciprocal 45.degree.
polarization rotator, according to an embodiment of the present
invention.
[0022] FIG. 2B is a plane view of a reciprocal 45.degree.
polarization rotator, according to an embodiment of the present
invention.
[0023] FIG. 3A is a cross-sectional view of a non-reciprocal
45.degree. polarization rotator, according to an embodiment of the
present invention.
[0024] FIG. 3B is a plane view of a non-reciprocal 45.degree.
polarization rotator, according to an embodiment of the present
invention.
[0025] FIG. 4A is a cross-sectional view of a phase compensator,
according to an embodiment of the present invention.
[0026] FIG. 4B is a plane view of a phase compensator, according to
an embodiment of the present invention.
[0027] FIG. 5 is a contour map of the electric field profile of the
propagating beam in a planar waveguide-type non-reciprocal
90.degree. polarization rotator without a phase compensator,
according to an embodiment of the present invention.
[0028] FIG. 6 is a plane view of an application scheme to an
optical isolator, according to an embodiment of the present
invention.
[0029] FIG. 7 is a plane view of another application scheme to an
optical isolator and circulator, according to an embodiment of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0030] Hereinafter, the present invention will be described in more
detail with reference to the accompanying drawings, in which
exemplary embodiments of the invention are shown.
[0031] An embodiment of the present invention is related to a
planar waveguide-type non-reciprocal polarization rotator which has
a low insertion loss and an excellent integration property with
laser diode and with other optical signal processing devices into a
single integrated device, and which can also be used for
application to optical isolator and circulator.
[0032] The present invention can be fabricated in a small
integrated optic device of non-reciprocal polarization rotator of
low insertion loss (IL) and high polarization extinction ratio
(PER), especially, in a monolithic integrated form of a planar
optical waveguide, contrary to the conventional monolithic
reciprocal polarization rotator and to the conventional
hybrid-integrated planar waveguide-type optical isolator, optical
circulator and non-reciprocal rotator.
[0033] FIG. 1 is a planar waveguide-type non-reciprocal 90.degree.
polarization rotator, according to an embodiment of the present
invention.
[0034] In FIG. 1, the planar waveguide-type non-reciprocal
90.degree. polarization rotator 100 formed on a semiconductor wafer
110 includes a reciprocal 45.degree. polarization rotator 200 and a
non-reciprocal 45.degree. polarization rotator 300. For a complete
polarization rotation, a phase compensator 400 can be added to
compensate the phase difference between the polarization modes of
the light beam passing the reciprocal 45.degree. polarization
rotator 200.
[0035] According to an embodiment of the present invention, the
planar waveguide-type non-reciprocal 90.degree. polarization
rotator includes optical waveguide-type input and output ports, a
reciprocal 45.degree. polarization rotator based on an asymmetric
optical waveguide structure, a non-reciprocal 45.degree.
polarization rotator based on an optical waveguide with a clad
layer of magneto-optic material, and a phase compensator placed
between the above reciprocal 45.degree. polarization rotator and
non-reciprocal 45.degree. polarization rotator compensating the
phase difference between two polarization modes.
[0036] The optical waveguide 120 in general optical waveguide
circuits usually has a pattern of low height and relatively wide
width (W1). When the optical waveguide 120 is connected to the
optical waveguides 130 and 210 of a relatively narrow width used
for the reciprocal 45.degree. polarization rotator, a tapered
optical waveguide 121 can be used to reduce the optical loss.
[0037] The reciprocal 45.degree. polarization rotator which is used
to form a planar waveguide-type non-reciprocal 90.degree.
polarization rotator is described in detail below.
[0038] FIG. 2A is a cross-sectional view of a reciprocal 45.degree.
polarization rotator, according to an embodiment of the present
invention. FIG. 2B is a plane view of a reciprocal 45.degree.
polarization rotator, according to an embodiment of the present
invention.
[0039] In FIG. 2A, the reciprocal 45.degree. polarization rotator
is composed of an optical waveguide 210 of height (H2) and width
(W2) of a similar dimension. One side of the optical waveguide 210
can be formed into an optical waveguide 211 etched in a square
shape of height (h2) and width (w2).
[0040] As illustrated in FIG. 2B, the etched waveguide 211 be
connected to the optical waveguide 210 with optical waveguides 212
of a tapered shape to reduce optical losses at optical beam input
and output sections. The planar waveguide devices are made of a
core material of low optical loss and of high refractive index, and
formed on a lower clad layer 110 of relatively low refractive index
which is usually made from an oxidation layer forming process on a
semiconductor wafer 111. Finally, an upper clad layer 220 of
relatively low index material needs to be formed for maintaining
uniform and reliable properties of the planar waveguide
devices.
[0041] The length of the optical waveguides 212 of tapered etch
shape needs to be optimized for a minimum optical loss, and the
height (h2) and width (w2) of the optical waveguide 211 etched in a
square shape also can be formed in optimum dimensions compared to
the height (H2) and width (W2) of the original waveguide 210 for
45.degree. polarization rotation.
[0042] The device operation is based on the principle of the
polarization rotation of the traveling beam due to birefringence
caused by the optical waveguides 210 with an etched side for the TE
and TM polarization modes.
[0043] The non-reciprocal 45.degree. polarization rotator which is
used to form a planar waveguide-type non-reciprocal 90.degree.
polarization rotator is described in detail below.
[0044] FIG. 3A is a cross-sectional view of a non-reciprocal
45.degree. polarization rotator, according to an embodiment of the
present invention. FIG. 3B is a plane view of a non-reciprocal
45.degree. polarization rotator, according to an embodiment of the
present invention.
[0045] In FIG. 3A, the non-reciprocal 45.degree. polarization
rotator 300 is composed of an optical waveguide 310 of height (H3)
and width (W3) of a similar dimension. An upper clad layer 320 of a
magneto-optic material is formed on the core optical waveguide 310,
and a magnetic field is applied by covering a magnetic material
layer 330. The width W3 and height H3 of the core optical waveguide
310 can be set to the same as the width W2 and height H2 of the
optical waveguide in the previous reciprocal 45.degree.
polarization rotator.
[0046] The upper clad layer 320 of magneto-optic material can be
made of magneto-optic polymer. For examples, the clad layer 320 can
be spin-coated with a polymer material of Fe.sub.3O.sub.4
core-polymer shell nanoparticle/PMMA matrix composites [Appl. Phys.
Lett. 95, 143302 (2009)] or of Regioregular poly(3 hexyl thiophene)
[Chem. Mater. 23, 516 (2011)], or formed with a layer of a
magneto-optic crystal, such as cerium-doped yttrium iron garnet
(Ce:YIG), bismuth europium holmium gallium iron garnet, or bismuth
yttrium iron garnet.
[0047] The top height (h3a) and side width (w3a) of the clad layer
320 of magneto-optic material can be determined for optimum values
by considering the magneto-optic coefficient of the MO material,
the magnitude of the applied magnetic field, and the length L3.
[0048] A bulk-type permanent magnetic or a plastic magnet can be
placed on the top of the upper clad layer 320 to apply a magnetic
field and to induce the polarization rotation in the magneto-optic
materials. Depending on the characteristics of the magnetic
material, the thickness (w3b) of the side wall can be included, or
only a top magnetic material layer 330 of a proper thickness (h3b)
can be formed.
[0049] As illustrated in FIG. 3B, the length L3 of the optical
waveguide covered with the magneto-optic material is determined to
a length causing a non-reciprocal 45.degree. polarization rotation
to a traveling light beam.
[0050] FIG. 4A is a cross-sectional view of a phase compensator,
according to an embodiment of the present invention. FIG. 4B is a
plane view of a phase compensator, according to an embodiment of
the present invention.
[0051] In FIG. 4A, a phase compensator 400, which is used to form
the planar waveguide-type non-reciprocal 90.degree. polarization
rotator, is placed between the above reciprocal 45.degree.
polarization rotator and non-reciprocal 45.degree. polarization
rotator to compensate the phase difference between two polarization
modes.
[0052] The phase compensator 400 compensates the phase difference
between TE and TM polarization modes, which results from the beam
passage through each of the reciprocal 45.degree. polarization
rotator 200 and non-reciprocal 45.degree. polarization rotator 300
in the non-reciprocal 90.degree. polarization rotator 100.
[0053] By using the difference between the effective indices of two
orthogonal polarizations with different width (W4) and height (H4)
of the optical waveguide, the phase of each polarization mode can
be controlled. This means that the overall polarization rotation
property of the non-reciprocal 90.degree. polarization rotator 100
can be optimized by controlling the length L4 of the phase
compensator 400.
[0054] In a case that the width (W4) of the optical waveguide 412
in the phase compensator 400 is different from those of the optical
waveguides connected at its both ends, tapered optical waveguides
411 are placed at both sides.
[0055] FIG. 5 is a contour map of the electric field profile of the
propagating beam in a planar waveguide-type non-reciprocal
90.degree. polarization rotator without a phase compensator,
according to an embodiment of the present invention shown in FIG.
1.
[0056] In FIG. 5, the electric field profiles of the beams
traveling to the opposite sides when incoming beams enter in the
forward and backward directions into the planar waveguide-type
non-reciprocal 90.degree. polarization rotator without a phase
compensator. The top figure of FIG. 5 shows the simulated result of
the TM-mode output from the left-hand side for a TM-mode input on
the right-hand side of the non-reciprocal 90.degree. polarization
rotator 100 without a phase compensator 400. The bottom figure of
FIG. 5 shows the simulated result of the TE-mode output from the
left-hand side after a 90.degree. polarization rotation for a
TM-mode input on the right-hand side.
[0057] FIG. 6 is a plane view of an application scheme to an
optical isolator, according to an embodiment of the present
invention.
[0058] In FIG. 6, an optical isolator scheme is shown for a TM
polarization mode by combining a pair of polarization beam splitter
and combiner with the planar waveguide-type non-reciprocal
90.degree. polarization rotator. Combination of the polarization
beam splitter and combiner 610 with coupled optical waveguides 620
at the both ends of the non-reciprocal 90.degree. polarization
rotator 100 acts as an optical isolator 600 for an input TM-mode
beam travelling from the right-hand side (Port 3) to the left-hand
side (Port 1) and for a reflected beam to the input.
[0059] The polarization beam splitter and combiner 610 consist of
polarization couplers using optical bridge waveguides 611. The
TM-mode beam travelling from the left-hand side (Port 1) to the
right-hand side passes the polarization beam splitter and combiner
610 and outputs through the right-hand side (Port 4) after
conversion to the TE-mode during the propagation through the
non-reciprocal 90.degree. polarization rotator. Thus, this device
acts as an optical isolator for a TM-mode input at the Port 3.
[0060] FIG. 7 is a plane view of another application scheme to an
optical isolator and circulator, according to an embodiment of the
present invention.
[0061] In FIG. 7, a polarization-independent optical isolator and
circulator is demonstrated with combining a pair of planar
waveguide-type non-reciprocal 90.degree. polarization rotators and
a pair of polarization beam splitter and combiner.
[0062] According to an embodiment of the present invention, the
planar waveguide-type non-reciprocal polarization rotator can act
as polarization-independent optical isolator by combining a pair of
the planar waveguide-type non-reciprocal 90.degree. polarization
rotators, each of which includes optical waveguide-type input and
output ports, a reciprocal 45.degree. polarization rotator based on
an asymmetric optical waveguide structure, a non-reciprocal
45.degree. polarization rotator based on an optical waveguide with
a clad layer of magneto-optic material, and a phase compensator
placed between the above reciprocal 45.degree. polarization rotator
and non-reciprocal 45.degree. polarization rotator compensating the
phase difference between two polarization modes, with a pair of
polarization beam splitter and combiner.
[0063] This scheme can be formed with a pair of the planar
waveguide-type non-reciprocal 90.degree. polarization rotators 100
and a pair of polarization beam splitter and combiner 610. In this
scheme, each of TE and TM-mode beams entering into Port 2 can
suffer a polarization rotation of 90.degree. by the non-reciprocal
90.degree. polarization rotators 100 and output through Port 3 on
the opposite side. The reflected beam into Port 3 does not suffer
any polarization rotation during passage through the non-reciprocal
90.degree. polarization rotators 100 in opposite direction, and
thus passes out through Port 1. Thus, this device can act as an
optical isolator and circulator.
[0064] According to an embodiment of the present invention, the
non-reciprocal 90.degree. polarization rotator can be fabricated
with a semiconductor device process, and formed with planar
semiconductor waveguides of easy integration and with a clad of
magneto-optic material to deliver a perfect polarization rotation
property and a low insertion loss over a broad operating wavelength
region.
[0065] According to another embodiment of the present invention,
the planar waveguide-type non-reciprocal polarization rotator is a
component of photonic integrated circuits, which can be easily
integrated with optoelectronic devices of various functions with
the conventional semiconductor process, and can be used in
applications to optical isolators and optical circulators.
[0066] It is understood that the embodiments and drawings described
herein are for illustrative purposes only and that various
modifications or changes are possible to persons who have a common
knowledge and skill in the art. For example, it will be evident
that the explained techniques can be implemented in different
orders according to the explained methods, and the explained
system, scheme, equipment, and circuit are combined or gathered, or
replaced with other components and equivalent items.
[0067] Thus, different demonstrations, embodiments and items
equivalent to what are claimed are belong to the inventions claimed
below:
* * * * *